A vehicle has a bumper at a front side of the vehicle for protecting a car body from external shock. The bumper includes a back-beam made of a metal having a predetermined level of rigidity, an energy absorber made of urethane to absorb shock and mounted on a front side of the back-beam, and a bumper cover covering the back-beam and the energy absorber.
Various bumpers are manufactured for vehicles to efficiently absorb shock energy in order to minimize injury to passengers and damage to main parts of the vehicles.
In general, the back-beam is coupled to front side members (also called “stays”) at both side of a front end module (FEM) having a radiator at a center through a crash box.
FIG. 1A is a perspective view illustrating an assembly of a back-beam and a crash box of the related art, and FIG. 1B is an exploded perspective view illustrating the crash box of a vehicle of the related art.
As illustrated in FIG. 1A, a crash box 2 of the related art is fixed by welding to the rear of a back-beam laterally disposed on a front side of a vehicle and absorbs shock energy of the vehicle.
In detail, as illustrated in FIG. 1B, the crash box 2 has a U-shape by pressing and includes an inner panel 2a and an outer panel 2b bonded by spot welding. The inner and outer panels 2a and 2b and the back-beam 1 are coupled by a bracket 3, and the inner and outer panels 2a and 2b and front side members (not illustrated) are coupled by a plate 4.
The crash box 2, the bracket 3, and the plate 4 are usually combined by butt welding using CO2, and in the figures, welding joints (indicated by straight lines) are formed between the crash box 2 and the bracket 3 and between the crash box 2 and the plate 4.
That is, the crash box of the related art is assembled by coupling the inner panel 2a and the outer panel 2b to the bracket 3 on the rear of the back-beam 1 using CO2 welding. The inner panel 2a and the outer panel 2b are combined using spot welding. The plate 4 is coupled to a rear side of the inner panel 2a and the outer panel 2b using CO2 welding.
However, in the crash box of the related art, the joints of the crash box, that is, the CO2-welded portions crack and break during the shock ability and durability test.
When the crash box breaks, shock energy is instantaneously cut and a car body cannot sufficiently absorb the shock energy, so the vehicle may further damaged and passengers may further injured.
Although it is possible to increase strength by double-welding the joints of the crash box in order to prevent such separation, it increases the manufacturing cost and decreases productivity.